Quizlet 2 - Chapter 7 Consolidation and Reconsolidation

interesting finding

-BUT what is happening in brain as episodic mems are being lost? -Determined that the hippocampus's response for pairs to which participants responded remember both at 10 minutes and 1 week (RR) and for pairs where participants responded remember at 10 minutes but know for 1 week (RK) = striking: --The hippocampus response remained high for RR pairs but dropped to near zero for RK pairs --Supports the idea that the hippocampus response changes over time, but only for stimuli that have lost their episodic character -So hippocampus responding is connected with episodic memories, which are still present a week after learning paris of pictures

practical outcome of reconsolidation research -> PTSD

-Brunet -> tested idea that reactivation of a memory followed by reconsolidation can help alleviate the symptoms of PTSD -Basic method involved is to reactive person's memory for traumatic event and administer drug propranolol --This drug blocks activation of stress hormone receptors in amygdala --Equivalent of administration of anisomycin on Day 2 in Nadar's experiment

opposition to hupbach's findings

-But Per Sederberg has proposed another explanation for Hupbach's results based on the temporal context model which does nto involve reconsolidation -According to TCM, for the reminder group, List A is associated with context on Monday, which includes experimenter 1 and blue basket -So the reconsoldiation explanation proposes that what is stored about the old memory has changed whereas the TCM explanation proposes that considering storage is unnecessary bc Hupbach's result can be explained by contextual associations

conditions

-Condition 1: rat receives the pairing of the tone and shock on day 1 which causes it to freeze --Antibiotic is injected right away before consolidation has occurred --On day 3 the rat still doesn't freeze to tone --Never received tone-shock pairing -Condition 2: rat receives the pairing of tone and shock on day 1 but doens't receive anisomycin until day 2 after consolidation has occurred --So still freezes -Condition 3: crucial condition --Creates situation where injects drug on day 2 (which had no effect in condition) can eliminate the memory of the tone-shock pairing --Present the tone on day 2 to reactivate the rat's memory for the tone-shock pairing --Rat freezes and then anisomycin is injected --Bc mem was reactivated by presenting the tone, the anisomycin now has an effect which is indicated by the fact the rat doesn't freeze on day 3

findigns

-Found that the propranolol group experienced much smaller increases in heart rate and skin conductance than the placebo group -Many of the PTSD patients reported significant reductions in their symptoms even months after treatment

Reconsolidation in humans -> Hupbach experiment

-Hupbach -> provided evidence for the effect of reactivation in humans using the following procedure in an experiment that involved two groups: the reminder group and the no-reminder group

findings

-Initially, measure a response and find a depolarization of a certain magnitude -Then apply the tetanic stimulation and find that the depolarization is much larger --It fades initially but stabilizes such that an hour later there doesn't appear to be much more fading going on after that (significant elevation still) -So experience of having a lot of stimulation on the synapse from that axon changes the performance of that synapse --This is a way of permanently making changes to the brain -> storage --Storage that can remain even without ongoing activity in the brain

So why does going to sleep shortly after learning enhance memory?

-One reason = that going to sleep eliminates environmental stimuli that might interfere with consolidation -Another reason = that consolidation appears to be enhanced during sleep --Evidence that some memories are more likely to be consolidated than others -See this is experiment by Wilhelm in which participants learned a task and were then told either that they would be tested on the task later or that they would be tested on a different task later

Reconsolidation rat experiment

-Possibility that retrieved memories can become fragile was demonstrated in rat experiment -Used classical conditioning to create fear response in the rat of "freezing" to presentation of a tone -Paired tone with a shock SO memory for the tone-sock pairing is indicated when rat freezes to the tone -In each of three conditions, rat receives a tone-shock pairing and is injected with an antibiotic that inhibits protein synthesis so prevents changes at the synapse that are responsible for formation of new mems -Key = when this is injected --If before consolidation has occurred, it eliminates mem --But if after consolidation, it has no effect

rat experiment for LTP

-Rat hippocampus experiment -Put a stimulating electron on an upstreaming axon and measure the electrical potential at the synapse downstream (that the axon is synapsing on) -So first you measure the response at the synapse to a single pulse of stimulation --How much does this synapse depolarize in response to one incoming action potential -Then you stimulate the heck out of the synapse by sending through the stimulating electrode a train of high intensity pulses -> te stimulation --And THEN you measure again the response to a single pulse and ask if there has been a change

Consolidation and sleep: enhancing memory

-Reactivation process associated with consolidation may begin as soon as a memory is formed, it is particularly strong during sleep -Gais tested idea that sleep enhances consolidation by having high school students learn a list of 24 paris of English-German vocab words --The sleep group studied the words and then went to sleep within 3 hours and the awake group studied the words and remained awake for 10 hours before getting a night's sleep --Both groups were tested within 24-36 hours after studying the vocab lists -Results of experiment indicate that students in the sleep group forgot much less material than students in the awake group

groups

-Reminder group --list of words --Come back wednesday with same experimenter and told to remember the same list and learn list b --Recall list a -No-reminder group --Learn list A --Come back with dif experimenter, not asked to recall list A and just to learn list b --Recall list a

what this shows

-Shows that when mem is reactivated, it becomes fragile just like when immediately was first formed -Thus just as original mem is fragile until it is consolidated for first time, a reactivated mem becomes fragile until it is reconsolidated -Mem is susceptible to being changed every time it is retrieved -Can be useful but also can be bad

findings

-The group that on wednesday was asked to recall list a while learning list b is more likely to intrude items from list b while recalling list a --Remembering items from list not supposed to be intruding -Interpretation: some of the words from day 2 got incorporated into memory of day 1 during reconsolidation --When you refreshed list a, caused it to reconsolidate and words experiencing in list b got into list a words

what this result indicates

-This result indicates that recalling memories activates a number of structures and most important for the purposes of the multiple trace model the hippocampus is activated even for remote memories

one way consolidation might work -> long term potentiation

-allows medial temporal lobe memory system to rapidly acquire and fix info such that this info can be held on to long enough to influence other forms of storage that can't acquire as quickly -so one general idea = medial temporal lobe rapidly acquired info then teaches it to rest of the brain

Consolidation

-defined as the process that transforms new memories from a fragile state in which they can be disrupted to a more permanent state in which they are resistant to disruption -is what happens between encoding and storage

Long term potentiation (textbook)

-enhanced firing of neurons after repeated stimulation -so the first time that neuron A is stimulated, neuron B fires slowly, however after repeated stimulation, neuron B fires much more rapidly to the same stimulus -this indicates that experiences can cause changes at the synapse

Gilboa's experiment

-experiment where elicited recent and remote episodic memories by showing participants photos of themselves engaging in various activities that were taken at times ranging from very recently to distant past when they were 5 years old -results = showed that the hippocampus was activated during retrieval of both recent and remote episodic memories

new memories are

-fragile -this was first shown by Muller and Pilzecker who did experiment in which two groups of participants learned lists of nonsense syllables --"immediate" group learned on list and then immediately learned a second list --"delay" group learned the first list and then waited 6 minutes before learning second list -when recall for the first list was measured, participants in the delay group remembered 48% of the syllables but participants in the immediate (no delay) group remembered only 28%

BUT this doesn't mean that the hippocampus is involved in all aspects of mem retrieval -> Viskontas showing response of HC changes over time

-had participants view pairs of stimuli like alligator and candle while undergoing fMRI in a scanner -Participants were told to imagine the items in each pair interacting with each other -Then 10 minutes laters and 1 week later, participants saw the original paris plus some others they hadn't see nad were told to respond to each pair in one of three ways: -1 - remember --Episodic -2 - know --Semantic 3 - don't know -Behavioral results show that there were more remember responses than know response after 10 minutes, but that only half of the remember responses remained after 1 week

What about autobiographical mems that retain their episodic character even after many years? -> Bonnici

-having participants recollect recent events in their lives which had occurred 2 weeks earlier and remotive events which occurred 10 years earlier --Told to report only events that they remembered very clearly -> episodic memories -Then asked to recall three of their recent mems and three of their remote mems --While brain scanned and after were asked to rate the vividness of the memory --fMRI responses associated with the most vivid mems were analyzed using multi voxel pattern analysis --Trained to determine the voxel pattern when participants were recalling each of their six memories (three recent and three remote) --Found that the classifier was able to predict which recent memories and which remote memories were being recalled based on activity in the hippocampus plus the prefrontal cortex and other cortical structures

The Standard model of consolidation

-hippocampus rapidly captures information and communicates with the cortex repeatedly over a time -bc of this repeated interaction, this leads to co-activation of areas in cortex and strengthens relations of areas in cortex -over time in standard model, HC drops out bc the cortical connections are sufficient to sustain the memory --so connections between the hippocampus and cortical areas weaken and connections between cortical areas strengthen until HC is no longer involved in those memories

can also relate to temporally grade amnesia

-idea is that infor that has a lot of opportunity to undergo systems of consolidation before injury is still able to be remembered after the injury -old stuff = remembered better bc not as affected by hippocampal damage

So when is HC important in the standard model?

-important / crucial during early stages of memory, as it is replaying the neural activity associated with the memory and sending this info to the cortex --this process = reactivation -> helps form direct connections between the various cortical areas -this model is based on observations of memory loss caused by injury

effects of consolidation and experience of remembering vs knowing

-initially encoded a word pair and were tested after 10 minutes and a week -after 10 minutes, were asked to say i remember, i know but don't have vivid experience of seeing it, or i don't know --half say they remember, 1/4 say know, and 1/4 say forgot --see large hippocampus response to both remember and know responses -BUT after a week, relatively few people experiencing vivid reflection and rest say more knows --just feel like they know it --look at MRI response and no longer see hippocampal response

neural circuits

-interconnected group of neurons

immediately presenting the second list of words did what to the immediate group

-interrupted the forming of a stable memory for the first list -based on this result, proposed consolidation term

Systems consolidation

-large scale brain networks -durations of days to years -replay -probably involved these rapidly acquired relationships being replayed by the medial temporal lobe system by rest of the brain -gradual reorganization of neural circuits within the brain

how can the brain store memories quickly but permanently?

-long term potentiation -> permanent change in synapses as result of previous stimulation --studied in hippocampus and important part of memory -Rat experiment (will come back to later)

Retrograde amnesia (textbook explanation)

-loss of memory for events that occurred before the injury and can extend back minutes, hours, or years -characteristic of this = graded amnesia -> amnesia tends to be most severe for events that happened just before the injury -this gradual decrease in amnesia corresponds, according to the standard model, to the changes in connections between the hippocampus and cortical areas and as time passes after an event, the cortical representation becomes stronger

what HM showed

-lost ability to form new memories after his hippocampus was removed indicates the importance of the hippocampus in forming new memories -once became clear that the hippocampus is essential for forming new memories, researchers began determining exactly how the hippocampus responds to stimuli and how it participates in the process of systems consolidation -see several methods proposed for what the role of the hippocampus is in memory

are they two separate stages?

-no -just bc synaptic consolidation is fast and systems consolidation is slower doesn't mean that we should think of them as two stages of a process that occur one after another like STM and LTM in modal model -more accurate to think of them as occurring together but at different speeds and at different levels of the nervous system -when something happens, a process is triggered that causes changes in synapse -meanwhile, a longer term process begins that involves reorganization of neural circuits -SO they happen at the same time -> one works rapidly at the level of the synapse and another works more slowly at the level of neural circuits

Wilhem's experiment

-participants learned a task and were then told either that they would be tested on the task later or that they would be tested on a different task later -After a night's sleep, participants in both groups were tested on the task to determine if what they expected had any effect on consideration -Memory performance after a night's sleep indicates that the expected group performed significantly better than the unexpected group -Thus even though both groups had the same training and received the same amount of sleep, memory for the task was stronger if participants expected they would be tested -So even though both groups had the same training and received the same amount of sleep, mem was stronger if expected to be tested

idea of memories being represented by a pattern of firing is similar to...

-population coding

forms of learning that aren't affected by damage to medial temp lobe mem system

-priming -procedural learning -conditioning -SO synaptic changes in one region don't underlie forms of all memory, but are specialized

Neural record of experience

-proposed that changes that occur in the hundred of synapses that are activated around the same time by particular experience provide a neural record of the experience -ex: New Year's eve, according to this idea, represented by the pattern of structural changes that occur at many synapses -Hebb's proposal that synaptic changes provide a record of experiences became the starting point for modern research on physiology of memory

The Multiple Trace Model of consolidation

-proposes that early in consolidation, the hippocampus communicates with cortical areas, however in contrast to standard model, the multiple trace model proposes that the hippocampus remains in active communication with cortical areas even for remote memories -HC has a continuing role even for remote memories -says that even for mems that are old and have these connections in cortex, connections in HC can still play role in determining behavior -see evidence in Gilboa's experiment

memories have a history

-right after event we remember many details of what learned -but with time some of these memories are lost or their character might change

Hebb's idea: repeated activity can strengthen the synapse by causing structural changes (synaptic consolidtation)

-said that learning and memory are represented in the brain by physiological changes that take place at the synapse -so assume a particular experience causes nerve impulses to travel down the axon of neuron A and when these impulses reach the synapse, neurotransmitter is related onto neuron B -his idea = that repeated activity can strengthen the synapse by causing structural changes, greater transmitter release, and increased firing

two types of consolidation

-synaptic consolidation -systems consolidation *both involve synapses and neural circuits

Synaptic consolidation

-takes place over minutes or hours, involves structural changes at synapses -local changes within brain systems (ex: hippocampus) due to phenomena like LTP (long term potentiation) which happens quickly -relatively shorter duration (minutes) -LTP

what researchers determined from Hebb's ideas

-that activity at the synapse causes a sequence of chemical reactions which result in synthesis of new proteins that cause structural changes at the synapse -one outcome of structural changes at the synapse = strengthening of synaptic transmission -> Long term potentiation

in class definition of consolidation

-the future vulnerability of a memory trace depends on how old that trace is - traces that have managed to survive for a time become less vulnerable to interference and thus decay less rapidly than younger traces

Reconsolidation

-the idea that when a memory is retrieved (remembered) it becomes fragile, like it was when it was originally formed and that when it is in this fragile state, it needs to be consolidated again -> process of reconsolidation -important bc when mem becomes fragile, it can be reconstructed -remembering can open door for modifying or forgetting

the medial temporal lobe memory system

-this kind of change (long term potentiation) is important for learning in the hippocampus and surrounding structures -> what we call medial temporal lobe memory system -it is specialized to make changes to store memory by making changes in synapse to permanently store memories -stores info by changes in synapses -may be critical for binding together components of an event -damage impairs the ability to form new episodic memories (amnesia) --if have damage, can't form new episodic memories --but some forms are much less affected

ran two groups

1 - PTSD patients listened to a 30 second recording describing the circumstances of their traumatic experience and received propranolol 2 - another group listened to the recording describing their experience but received a placebo which had no active ingredients -One week later, both were told to imagine their traumatic experience while again listening to the 30 second recording -To determine their reaction to imaging their experience, measured blood pressure and skin conductance

secondary findings

1 - more info about remote memories compared to recent memories was contained in the prefrontal cortex 2 - information about both recent and remote memories was represented throughout the hippocampus, with the posterior hippocampus containing more info about remote memories -Taken together, these results show that remote memories are richly represented in the cortex, as proposed by both the standard and multiple trace models and that both recent and remote memories are represented in the hippocampus as well